Research On Underwater Acoustic Multicarrier Communication Technology Based On Index Modulation

Underwater acoustic communication is a hot research content in signal and information processing field.It has been widely concerned by domestic and foreign researchers,and it is a rapid development of scientific research field.However,as the underwater acoustic channel is a complex time-space frequency varying channel,it has the characteristics of narrow bandwidth,serious signal attenuation and strong multipath effect,which is easy to be interfered by many factors,which greatly limits the development of underwater acoustic communication.Therefore,it is of great significance to find an anti-interference communication technology suitable for the underwater acoustic environment.Because of its good anti-interference capability in underwater acoustic channel,FBMC(Filter Bank Multi Carrier)technology has become the main high-speed underwater acoustic multicarrier communication mode.But FBMC has many disadvantages,such as the inherent virtual interference between symbols and subcarriers,which makes the system unable to obtain better transmission performance.In order to improve the performance of underwater acoustic communication system,this thesis applies index modulation(IM)to FBMC system,and proposes a new system.The improvement of the communication system greatly improves the BER performance of the system,and makes the system more suitable for the complex underwater communication.The main research contents are as follows:1.For the traditional FBMC system can not obtain the optimal communication performance in underwater acoustic communication,this thesis combines index modulation with FBMC technology,and proposes FBMC modulation method based on index modulation(FBMC-IM).This method uses index information to selectively activate subcarriers,so as to improve the communication performance of the system by adjusting the number of real subcarriers and empty subcarriers.Finally,the simulation results show that the system can not only weaken the interference energy,improve the BER performance of the system,but also ensure the spectral efficiency of the system.2.In order to improve the transmission performance of the new FBMC-IM system,the optimization design and channel estimation method are studied in this thesis.In order to reduce the impact of interference on the system,the maximum Hamming distance and the minimum bad combination principle are proposed respectively,and the optimal subcarrier group is selected by these two principles;In order to map the index information to the selected optimal subcarrier group,an optimal combination mapping criterion is proposed to optimize the system.Considering that the inherent imaginary interference in the system increases the difficulty of channel estimation,several channel estimation methods of FBMC-IM system are studied and analyzed,and a more suitable channel estimation method is found.3.In order to further improve the BER performance of FBMC-IM system,an interleaved subcarrier index modulation system based on filter bank multicarrier(FBMC-ISIM)is proposed.The system interleaves the subcarriers after index modulation on the basis of FBMC-IM system,which is equivalent to adding equal interval interleaver in frequency domain,so that each subcarrier is weakened and uncorrelated.Finally,the simulation results show that FBMC-ISIM system has better BER performance.